Function convertFlatToTree

src/utils/tree.ts:31–56

(items: T[])

 * @returns A tree structure with children property
 */
export function convertFlatToTree<T extends { id: string; parentId: string }>(items: T[]): (T & { children: T[] })[] {
	const itemMap = new Map<string, T & { children: T[] }>();
	const result: (T & { children: T[] })[] = [];

	// First pass: create a map of all items
	for (const item of items) {
		itemMap.set(item.id, { ...item, children: [] });
	}

	// Second pass: build the tree
	for (const item of items) {
		const node = itemMap.get(item.id);
		if (!node) continue;

		if (item.parentId === "") {
			result.push(node);
		} else {
			const parent = itemMap.get(item.parentId);
			if (parent) {
				parent.children.push(node);
			}
		}
	}

	return result;
}